A Tale of Two Solanums, or, Plant ID Practice

I have two nightshade - solanum - type plants growing wild around here.

There's a pretty one. The flowers are a bit more blue than they look here:


and an ugly one. Well it's ugly partly because it spreads everywhere mixed in with other things and is straggly in its growth habit:


And I want to know if they are weedy or not, and native or not. I’m going to try and ID them all by myself.

I think they are solanum because I recognize the type of flower and the berries. Perverse as it sounds, I think recognition is key to IDing plants, at least when you're not very good at it. You have to have a working hypothesis or you're sunk.

I assemble my materials:

• Thomas - Flora of the Santa Cruz Mountains
• Jepson – Be all and end-all reference for California native plant enthusiasts, newly acquired
• Weeds of the West.
• And the internet. - calflora.org, laspilitas.com

First problem – eight of the species listed in Thomas are not listed in Jepson. Have the names changed so much?

Second problem: all solanum species are included. Had any mashed tubers of Solanum tuberosum for dinner lately?

OK, so I try the dichotomous key approach using Thomas, to ID the pretty one. A dichotomous key gives you two choices at every step. Is it this? Yes or no.

The first bifurcation is: is it spiny or not? No, they are not spiny who grow here I believe - I would have felt the spines.

Next: "Leaves simple" – yup. Kind of an oval shape. I follow down to the next question. "Corollas blue" - check.

Then I get stuck. It's all in botanese. What is "suffrutescent?" I know about as much Botanese as I know Spanish – which is to say not much. Plus they abbreviate all over the place. Great if you know what’s what. I'm frustrated. This is taking ages. It's sunny outside.

I go out and look at the plants again. But now I'm more observant. About the blue pretty one I muse: Leaves entire. Petiolate. Alternate. Green, not gray foliage. Flowers in umbels. (Look at me - I'm speaking in broken Botanese!) Flowers 1/4 to 1/2 inch across. Yellow in the middle and - Hm. Didn’t notice those little green spots at the very base of the petal before...


The plant as a whole has been nibbled, but even so you can tell it has a very compact form, upright but densely branching. I hope the nibblers aren't dead, because after all, this is the nightshade family. And on looking up "suffrutescent" I find it means "somewhat shrubby."


Now the ugly one with white flowers. Oh, teeny tiny flowers! much less than 1/4 inch across.


And black berries, and very straggly in growth leaves toothed and messy looking. I hope it isn't a native because - this is not an attractive plant.


So now I try a visual approach. First I look through Weeds of the West, which has lots of full-size color pictures of weeds. You have to bear in mind that a "weed" is in the mind of the beholder, and they ID various natives as weeds because they are more interested in range management and agriculture.

Oh, ugly one looks a lot like Solanum Nigrum, a nasty invasive.

Next I go to calflora.org and search on all solanum species native or not, in Santa Cruz County. Oh, not so many!

There it is! The pretty blue one is S. umbelliferum - Blue Witch, a native.

But the white one could also be S. americanum. Which is it? S. nigrum or S. americanum?

So Back to Jepson, to check the hypotheses so far. This is how I've been finding the keys useful - to check a hypothesis, rather than to start from scratch.

On S. umbelliferum – Jepson notes flowers "with 2 greenish spots at base" - Maybe my example has only one greenish spot? Hard to tell. I don't care by now. But for S. umbelliferum it says "hairs gen dense," and I didn't see no stinkin' hairs dense or otherwise. Hm. Maybe I'm wrong. But now I look at my own photo more closely I see very very tiny hairs.

This back and forthing is definitely making me more observant.

And there are also subspecies and they hybridize - vars. glabrescens and incanum. Glabrous is a term I've heard of before. Thomas’s glossary says, "Glabrous: Lacking hairs or pubescence." So I'm not really sure if it's S. umbelliferum, or if it's S. umbelliferum glabrescens, but we are now splitting hairs and at this point I don't care a lot. I'm happy it's a worthy native and I'm glad it has found a home in our chaparral area.

On the white flowered one Jepson is really helpful in deciding if it's S. nigrum or S. americanum.

S. nigrum is hairy, my sample is not. Its corollas are 10mm across - my sample definitely less than a centimeter. And - oops. I didn't notice that S. nigrum occurs only up to 200 meters above sea level. We are at about 300 meters.

S. americanum is not hairy. It occurs at 1000 meters or less. And its corollas: 3-6 mm across!

So the small white flowered solanum is S. americanum. It is found all over America, and may be an early introduction from South America. So though it's native to America as a whole - I am comfortable considering it as a weed for my purposes. It is crowding out my local natives in the shady north side of our property and elsewhere.

Well an hour or two of patient sleuthing gave me pretty good results. Of course if I could have talked with an experienced plant geek, I'd have had my answer in 2 minutes flat! But unfortunately plant geeks don't grow on trees. They share themselves around as best they can, however, in books, and they speak Botanese to do so. Glabrous and suffrutescent: Two marvelous new Botanese words for my delectation and delight. And two marvelous identifications to help me on my way.

Next in line - IDing the native California spurge and the non-native spurge - as a spurge scourge is happening on my property everywhere the Oxalis pes-caprae is not!


Ed: Feb 2014. I didn't key the spurge, but I did just work on what Ribes is growing in the north valley. You can see that post here, if you like this sort of thing.